A system comprised blocks, a light frictionless pulley, and connecting ropes is shown in the figure. The
9.0-kg
block is on a perfectly smooth horizontal table. The surfaces of the
12-kg
block are rough, with
\mu _(k)=0.30
between the block and the table. If the
5.0-kg
block accelerates downward when it is released, find its acceleration. 2 A) B) C) D) E)